It is known to use a coding pattern to embed some type of information in a passive base such as a sheet of paper, a writing board or equivalent. A suitably programmed scanner, fax machine, camera or digital pen can then read, recreate and use the information embedded locally in the base. For example, graphical information on a base can be supplemented with embedded information which extends the functionality of the base. Such embedded information can comprise file data for full or partial recreation of the graphical information, commands, supplementary text or images, hyperlinks, absolute positions, etc.
Coding patterns are generally constructed around some form of machine-readable code symbols which are regularly spaced on the base. One specific class of coding patterns are based on one or more cyclic number sequences, also called pseudo-random sequences. As is known, such a cyclic number sequence is the ordered set of unique n-bit long subsequences that an n-stage shift register generates when it is preloaded with a given seed value and operated with feedback taps at specified register locations. Thus, such a cyclic number sequence has the property that the place in the number sequence of each subsequence of a predetermined length (n) is unambiguously determined. According to various principles, data may encoded on the base by printing such a cyclic number sequence, in the form of a sequence of graphical symbols, over the base surface with various rotations or circular shifts. Different encoding principles are described, i.a., in WO 92/17859; WO 00/73983; WO 01/26032; WO 01/71643; WO 02/084473; WO 03/001440; U.S. Pat. No. 6,000,621; and U.S. Pat. No. 6,208,771.
In many cases, bases with a coding pattern can be generated on a large scale and with high precision in the graphics industry. There are, however, also occasions when it is desirable to create bases with a coding pattern on a small scale, for example by using a personal computer, to which a printer of, for example, the ink-jet or laser type, has been connected.
This can be carried out in such a way that the required coding pattern is created as an image file in a graphical format, for example, in bitmap format. This image file is converted by the computer into a page-describing and normally printer-independent code, such as PostScript (trademark), after which it is transmitted to the printer unit. On the basis of the page-describing code, the printer unit creates corresponding instructions for control of the printer's hardware. This hardware can, in the case of a laser printer, comprise a laser diode with associated optics. In an ink-jet printer, the hardware may comprise an ink ejector arrangement. The printing is then carried out on a base, for example a sheet of paper.
If the coding pattern has a high information density, which can be achieved by dense arrangement of the code symbols on the base, the image file and the page-describing code may become large. Consequently, transfer times and printer processing times for such code may become excessive.